Lithium-ion batteries and power consuming devices

Abstract

A lithium ion battery and a power consumption device including the same, the lithium ion battery includes a positive electrode, a negative electrode, and an electrolyte, the negative electrode includes a negative electrode current collector, and a negative electrode active material layer including a negative electrode active material attached to at least one surface of the negative electrode current collector, the average width:length ratio of the particles of the negative electrode active material is 0.1-1, the ionic conductivity of the electrolyte is 7-15mS / cm, and the ratio CB of the lithium absorption capacity of the negative electrode to the lithium desorption capacity of the positive electrode is 1.05-1.5. The lithium ion battery has a high-rate rapid charging capability and good cycle performance.

Description

[Technical field]

[0001] This application relates to the field of lithium battery technology, and in particular to lithium ion batteries and power consuming devices. [Background technology]

[0002] In recent years, as the application scope of lithium ion batteries becomes wider and wider, lithium ion batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, as well as in multiple fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. However, compared with traditional fuel oil-driven devices, problems such as range anxiety and long charging time have become major problems that hinder the development of secondary batteries, and how to improve the rapid charging ability of secondary batteries is one of the focuses of those skilled in the art.

[0003] Improving the fast charging capability of batteries is a system engineering that requires changing and upgrading battery materials. In the past, most research has been done on improving the negative electrode material, but at the same time, it is necessary to mix materials such as electrolyte and conductive agent. Therefore, conventional batteries with fast charging capability need to be further improved. Summary of the Invention

[0004] The present application has been made in view of the above problems, and its objective is to provide a lithium ion battery, which comprises an average negative electrode active material with a specific width:length ratio, an electrolyte with a specific ionic conductivity, and has a ratio CB of the lithium absorbing capacity of the negative electrode to the lithium releasing capacity of the positive electrode within a specific range, so that the battery has a high-rate fast charging capability and good cycle performance.

[0005] To achieve the above objective, the present application provides a lithium ion battery and a power consuming device.

[0006] A first aspect of the present application provides a lithium-ion battery including a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode includes a negative electrode current collector, and a negative electrode active material layer including a negative electrode active material deposited on at least one surface of the negative electrode current collector, wherein an average width:length ratio of particles of the negative electrode active material is 0.1 to 1, the ionic conductivity of the electrolyte is 7 to 15 mS / cm, and a ratio CB of the lithium absorption capacity of the negative electrode to the lithium desorption capacity of the positive electrode is 1.05 to 1.5.

[0007] The lithium ion battery of the present application comprises an average negative active material with a specific width:length ratio, an electrolyte with a specific ionic conductivity, and has a ratio CB between the lithium storage capacity of the negative electrode and the lithium desorption capacity of the positive electrode within a specific range, thereby effectively reducing the internal curvature of the negative electrode plate, improving the liquid phase transport conditions of lithium ions, and providing more active sites in the negative electrode for storing lithium ions, thereby improving the high-rate fast charging ability and cycle performance of the battery.

[0008] In any of the embodiments, the battery has a current that is 4 times or more the lithium extraction capacity of the positive electrode per unit time during charging from 0% to 70% at 35° C., thereby further improving the high-rate fast charging capability and cycle performance of the battery.

[0009] In one embodiment, the average current during charging of the battery from 0% to 80% at 35° C. is at least four times the lithium release capacity of the positive electrode per unit time, thereby further improving the high-rate fast charging capability and cycle performance of the battery.

[0010] In any of the embodiments, the porosity of the negative electrode active material layer is 20-60%, thereby providing more active sites in the negative electrode for absorbing more lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0011] In any one of the embodiments, the negative electrode active material layer has a compaction density of 1.2 to 1.9 g / cm. 3 The coating weight is 5 to 18 mg / cm 2 Thereby providing more active sites in the negative electrode for further absorbing lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0012] In any of the embodiments, the negative electrode active material comprises natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon, silicon-carbon composite, silicon oxide, or a composition thereof, thereby providing more active sites in the negative electrode for storing more lithium ions, thereby improving the high-rate fast charging capability and cycling performance of the battery.

[0013] In any of the embodiments, the thickness of the negative electrode active material layer is 30-150 μm, which further improves the liquid phase transport conditions of lithium ions and provides more active sites in the negative electrode for absorbing lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0014] In any of the embodiments, the active material layer includes a first active material layer including a first negative electrode active material, and a second active material layer including a second negative electrode active material deposited on a surface of the first active material layer away from the current collector, thereby further improving the liquid phase transport conditions of lithium ions and providing more active sites in the negative electrode for absorbing lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0015] In any one of the embodiments, the first negative electrode active material has an average volume particle size D v50 is the average volume particle diameter D of the second negative electrode active material v50 , thereby providing more active sites in the negative electrode for further lithium ion storage, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0016] In either embodiment, the first negative electrode active material layer has a greater packed density than the second negative electrode active material layer, thereby providing more active sites in the negative electrode for storing additional lithium ions, thereby improving the high-rate fast charging capability and cycling performance of the battery.

[0017] In any of the embodiments, the electrolyte solution comprises a lithium salt, a solvent and an additive, where the lithium salt comprises a main lithium salt and a secondary lithium salt, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0018] In any of the embodiments, the primary lithium salt is different from the secondary lithium salt, and the primary lithium salt or secondary lithium salt is each independently selected from at least one of LiPF6, LiN(SO2F)2, LiBF4, LiN(CF3SO2)2, LiClO4, LiAsF6, LiB(C2O4)2, LiBF2C2O4, lithium difluorobis(oxalato)phosphate, LiPO2F2, LiFSO3, and LiF, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0019] In any of the embodiments, the primary lithium salt is lithium hexafluorophosphate or LiFSI, the content of which is 8-20 wt% based on the total weight of the electrolyte, and the secondary lithium salt is at least one of lithium difluoro(oxalato)borate, LiBF4, LiB(C2O4)2, and lithium difluorobis(oxalato)phosphate, the content of which is 0.001 wt%-2 wt% based on the total weight of the electrolyte, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0020] In any of the embodiments, the solvent includes a cyclic ester and a linear ester, the cyclic ester content being 5-40% by mass of the solvent and the linear ester content being 60-95% by mass of the solvent, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0021] In any of the embodiments, the cyclic ester is ethylene carbonate, propylene carbonate, or a combination thereof, and the linear ester includes dimethyl carbonate, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0022] In any of the embodiments, the linear ester is selected from diethyl carbonate, methyl ethyl carbonate, methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, or combinations thereof, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0023] In any of the embodiments, the percentage b% of the linear ester in the solvent relative to the solvent mass and the ionic conductivity a (mS / cm) of the electrolyte satisfy the relationship 8≦a+3b%≦16, which further improves the liquid phase transport conditions of lithium ions and provides more active sites in the negative electrode for absorbing lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0024] In one embodiment, the positive electrode comprises a current collector and a positive electrode active material layer deposited on at least one surface of the current collector, the positive electrode active material having the formula LiNi x Co y Q z M 1-x-y-zO2 ternary material, where Q is Mn or Al, M is at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, and 0≦x<1, 0≦y≦1, 0≦z≦1, and x+y+z≦1, thereby further improving the liquid phase transport conditions of lithium ions and providing more active sites in the negative electrode for absorbing lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0025] A second aspect of the present application provides a power consuming device comprising the secondary battery described in the first aspect of the present application.

[0026] The lithium ion battery of the present application includes an average negative electrode active material with a specific width:length ratio, an electrolyte with a specific ionic conductivity, and has a ratio CB between the lithium storage capacity of the negative electrode and the lithium release capacity of the positive electrode in a specific range, thereby improving the liquid phase transport conditions of lithium ions and providing more active sites in the negative electrode for storing lithium ions, thereby improving the high-rate fast charging ability and cycle performance of the battery. [Brief description of the drawings]

[0027] [Figure 1] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Diagram 2] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. [Diagram 3] 1 is a schematic diagram of a power consumption device that uses a secondary battery as a power source according to an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, with appropriate reference to the drawings, an embodiment specifically disclosing the lithium ion battery and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of structures that are actually the same may be omitted. This is to avoid the following description becoming unnecessarily long and to allow those skilled in the art to easily understand. Note that the drawings and the following description are provided to allow those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0029] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also envisaged. It is noted that if 1 and 2 are listed as the minimum range values, and 3, 4, and 5 are listed as the maximum range values, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all envisaged. In this application, unless otherwise specified, a numerical range "a-b" represents a shorthand representation of any combination of real numbers a-b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" already listed in this specification, and "0-5" is merely a shorthand for combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0030] Unless otherwise stated, all the embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0031] Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0032] Unless otherwise stated, all steps in this application may be performed in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, the method mentioned above may further include step (c) means that step (c) may be added to the method in any order, such as the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0033] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may further include or include other ingredients not listed, or may include or include only the listed ingredients.

[0034] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the following conditions satisfy "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and A and B are both true (or exist).

[0035] Currently, compared with conventional fuel-powered devices, issues such as uncertainty about driving range and long charging times have become major problems hindering the development of secondary batteries, and how to improve the rapid charging capability of secondary batteries is one of the focuses of attention of those skilled in the art.

[0036] Improving the fast charging ability of a battery is a system engineering that requires changing and upgrading the materials of the battery. In the prior art, the most researched is the improvement of the negative electrode material, but at the same time, the blending of materials such as electrolyte and conductive agent is required. Therefore, the conventional battery with fast charging ability needs to be further improved. The inventor has found through research that the lithium ion battery of the first embodiment of the present application comprises a negative electrode active material with a specific average width:length ratio, an electrolyte with a specific ion conductivity, and has a specific range of the ratio CB between the lithium absorption capacity of the negative electrode and the lithium desorption capacity of the positive electrode, whereby the average width:length ratio of the negative electrode active material particles is adjusted to effectively reduce the internal curvature of the negative electrode plate, increase the conductivity of the electrolyte, and greatly improve the liquid phase transport conditions of lithium ions, and the relatively high CB value provides more active sites in the negative electrode for absorbing lithium ions, thereby improving the high-rate fast charging ability and cycle performance of the battery.

[0037] Lithium-ion battery In some embodiments, a first aspect of the present application provides a lithium-ion battery including a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer including a negative electrode active material deposited on at least one surface of the negative electrode current collector, wherein an average width:length ratio of particles of the negative electrode active material is 0.1 to 1, and optionally 0.6 to 1; an ionic conductivity of the electrolyte is 7 to 15 mS / cm, and optionally 8 to 13 mS / cm, and more optionally 9 to 11 mS / cm; and a ratio of the lithium absorption capacity of the negative electrode to the lithium desorption capacity of the positive electrode, C, measured according to HG / T4067-2015, is 1.05 to 1.5, and optionally 1.1 to 1.3, and more optionally 1.1 to 1.2.

[0038] The lithium ion battery of the present application comprises an average negative active material with a specific width:length ratio, an electrolyte with a specific ionic conductivity, and has a ratio CB between the lithium storage capacity of the negative electrode and the lithium desorption capacity of the positive electrode within a specific range, thereby effectively reducing the internal curvature of the negative electrode plate, improving the liquid phase transport conditions of lithium ions, and providing more active sites in the negative electrode for storing lithium ions, thereby improving the high-rate fast charging ability and cycle performance of the battery.

[0039] In the present application, the "width:length ratio" of the negative active material is the ratio of the shortest diameter to the longest diameter of the negative active material particles. The width:length ratio of the negative active material can be obtained by dynamic particle image analysis (e.g., using a Sympatec QICPIC dynamic particle image analyzer). The "short diameter" of the negative active material particles is the minimum value between parallel lines tangent to a projected image of the particle. The "long diameter" of the negative active material particles is the maximum value between parallel lines tangent to a projected image of the particle. When the width:length ratio of the negative active material is relatively small, the negative active material particles have an elongated shape, and when it is close to 1, the negative active material particles have a spherical shape.

[0040] In this application, the ionic conductivity of the electrolyte means the ability of the electrolyte to conduct electricity. In this application, the term "lithium release capacity of the positive electrode" refers to the actual lithium release capacity of the positive electrode material in the battery. The test method is as follows: In a PRS340 / 11-119-11 MBRAUN robe box, the battery is disassembled, the positive electrode plate is taken out, and the positive electrode-lithium piece is assembled into a CR2430 type half coin battery. The area of ​​the positive electrode plate used is a mm 2Here, the electrolyte is a solution of 1M LiPF6 used with EC / EMC / DEC=3 / 5 / 2, and the assembled half coin cell is left to stand for 3 hours and tested at 25°C. First, charge at 0.1C in the voltage range of 2.5~eV to perform lithium desorption, where e is the upper limit voltage of the cell design, and discharge at 0.05C to 2.5V to perform lithium absorption. Then, cycle twice. The discharged coin cell capacity in the second cycle is Y mAh. The length of the positive electrode film in the actual battery design is b mm, the width is c mm, and the number of surfaces coated with the positive electrode active material on the positive electrode current collector is d. The lithium desorption capacity of the positive electrode is X=Y / a*b*c*d.

[0041] In some embodiments, the lithium release capacity of the positive electrode is 2000 to 300000 mAh, optionally 3000 to 150000 mAh, and further optionally 3000 to 4000 mAh.

[0042] In this application, the term "lithium storage capacity of the negative electrode" refers to the actual lithium storage capacity of the negative electrode material in the battery. The test method is as follows: In a PRS340 / 11-119-11 MBRAUN robe box, the battery is disassembled, the negative electrode plate is taken out, and the negative electrode-lithium piece is assembled into a CR2430 type half coin battery. The negative electrode plate area used is f mm 2 Here, the electrolyte is a solution of 1M LiPF6 used in EC / EMC / DEC=3 / 5 / 2, and the assembled half coin cell is left to stand for 3 hours and tested at 25°C. First, discharge at 0.1C in the voltage range of 2V~0V to absorb lithium, and then charge at 0.05C to 2V to release lithium. The cycle is repeated twice, and the discharged coin cell capacity in the second cycle is Z mAh. The length of the negative electrode film in the actual battery design is h mm, the width is i mm, and the number of surfaces coated with the negative electrode active material on the negative electrode current collector is d. The lithium release capacity of the negative electrode is W=Z / f*h*i*d.

[0043] In some embodiments, the lithium storage capacity of the negative electrode is 2100 to 315000 mAh, optionally 3000 to 100000 mAh, and further optionally 3500 to 4500 mAh.

[0044] In some embodiments, the battery has a current of 4 times or more the lithium desorbable capacity of the positive electrode per unit time during charging from 0% state of charge (SOC) to 70% state of charge (0-70% SOC) at 35°C, optionally the current is 5 times or more the lithium desorbable capacity of the positive electrode per unit time, and optionally 5 to 6.5 times the lithium desorbable capacity of the positive electrode per unit time. This further improves the high-rate quick charge capability and cycle performance of the battery. In this embodiment, the current is an instantaneous current.

[0045] In this application, "lithium release capacity of the positive electrode per unit time" means the amount of lithium released from the positive electrode per unit time (1 h), and the average current generated in this process is used as the basis for current quantization in this application, so that the lithium release capacity of the positive electrode can be related to the current.

[0046] In some embodiments, in the process of charging from 0% charge state to 70% charge state at 35°C, a constant current DC charging method may generally be used, for example, a current of the positive electrode's desorption / absorption capacity in a unit time of 4 times is used to charge from 0% charge state to 70% charge state, and a stepwise charging method may be used, for example, 0-10% SOC uses a current of the positive electrode's desorption / absorption capacity in a unit time of A times, 10-20% SOC uses a current of the positive electrode's desorption / absorption capacity in a unit time of B times, and 20-30% SOC uses a current of the positive electrode's desorption / absorption capacity in a unit time of B times. A uses a current of C times the positive electrode's desorption / absorption capacity in a unit time, 30-40% SOC uses a current of D times the positive electrode's desorption / absorption capacity in a unit time, 40-50% SOC uses a current of E times the positive electrode's desorption / absorption capacity in a unit time, 50-60% SOC uses a current of F times the positive electrode's desorption / absorption capacity in a unit time, 60-70% SOC uses a current of G times the positive electrode's desorption / absorption capacity in a unit time, etc., where at least one of A, B, C, D, E, and F is not 4. As can be understood by those skilled in the art, in the stepwise charging method, the stepwise SOC and current magnitude can be adjusted as necessary.

[0047] For the already packaged battery, the positive electrode lithium release capacity detection method is used to test to obtain the positive electrode lithium release capacity X, the battery is charged using the above charging mode, and then disassembled to take out the positive electrode plate, and the positive electrode lithium release capacity detection method is used to test to obtain the positive electrode lithium release capacity Z at this time, and if Z / X≧40%, it is considered to meet the charge rate of the positive electrode lithium release capacity within 4 times the unit time.

[0048] In some embodiments, the average current during charging of the battery from 0% SOC to 70% SOC at 35° C. is at least 4 times the lithium desorption capacity of the positive electrode per unit time, and optionally at least 5 times the lithium desorption / absorption capacity of the positive electrode per unit time, thereby further improving the high-rate fast charging capability and cycle performance of the battery.

[0049] In one embodiment, when the test method for average current from 0 to 70% SOC uses a constant current DC charging method, the average current is the charging current, and when the stepwise charging method described above is used, the average current is (A+B+C+D+E+F+G) / 7.

[0050] In some embodiments, the porosity of the negative electrode active material layer is 20-60%, optionally 25-40%, and more optionally 25-31%, thereby providing more active sites in the negative electrode for absorbing more lithium ions, thereby improving the high-rate fast charging capability and cycling performance of the battery.

[0051] In some embodiments, the negative electrode active material layer has a compaction density of 1.2 to 1.9 g / cm 3 and optionally, 1.5 to 1.78 g / cm 3 The coating weight is 5 to 18 mg / cm 2 Thereby providing more active sites in the negative electrode for further absorbing lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0052] In some embodiments, the active material layer comprises a first active material layer including a first negative electrode active material and a second active material layer including a second negative electrode active material deposited on a surface of the first active material layer away from the current collector, thereby further improving the liquid phase transport conditions of lithium ions and providing more active sites in the negative electrode for absorbing lithium ions, thereby improving the high-rate fast charging capability and cycling performance of the battery.

[0053] In some embodiments, the first negative electrode active material has an average volume particle size D v50 is the average volume particle diameter D of the second negative electrode active material v50 , thereby providing more active sites in the negative electrode for further lithium ion storage, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0054] In some embodiments, the first negative electrode active material has an average volume particle size D v50 is 10 to 20 μm, optionally 12 to 16 μm, and the average volume particle size D of the second negative electrode active material v50 is 9-19 μm, and is measured based on particle size distribution laser diffraction method (see GB / T19077.1-2009).

[0055] In some embodiments, the first negative electrode active material layer has a thickness of 10 to 120 μm, and the second negative electrode active material layer has a thickness of 10 to 120 μm, which is measured based on ion polishing cross-sectional morphology analysis by scanning electron microscopy (see JY / T010-1996 for details) (at least five points are measured and the average value is taken).

[0056] In some embodiments, the negative electrode active material comprises natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon, silicon-carbon composite, silicon oxide, or a composition thereof, thereby providing more active sites in the negative electrode for storing more lithium ions, thereby improving the high-rate fast charging capability and cycling performance of the battery.

[0057] In some embodiments, the thickness of the negative electrode active material layer is 30-150 μm, which can further improve the liquid phase transport conditions of lithium ions and provide more active sites in the negative electrode for absorbing lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0058] In some embodiments, the first negative electrode active material layer has a packed density greater than the packed density of the second negative electrode active material layer, thereby providing more active sites in the negative electrode for storing additional lithium ions, thereby improving the high-rate fast charging capability and cycling performance of the battery.

[0059] In some embodiments, the first negative electrode active material layer has a compaction density of 1.3 to 2 g / cm3 and the compaction density of the second negative electrode active material layer is 1.2 to 1.9 g / cm 3 The mass of the negative electrode material layer was weighed on a standard balance, the coating area of ​​the negative electrode plate was measured with a ruler, and the unit area mass of the negative electrode material layer, i.e., the density of the coating surface CW (mg / cm 2 ) can be calculated. Then, the thickness of the negative electrode material layer is measured (at least five points are measured and the average value is taken) by ion polishing cross-sectional morphological analysis using a scanning electron microscope (see JY / T010-1996), and the compaction density of the coating film = the density of the coating surface of the negative electrode plate CW (mg / cm 2 ) / thickness (cm) of the negative electrode material layer, calculate the compaction density PD (unit: mg / cm 3 ) and g / cm 3 Measured in units of 10 ...

[0060] In some embodiments, the electrolyte comprises a lithium salt, a solvent and an additive, where the lithium salt comprises a primary lithium salt and a secondary lithium salt, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0061] In some embodiments, the primary lithium salt is different from the secondary lithium salt, and the primary lithium salt or secondary lithium salt is independently selected from at least one of LiPF6, LiN(SO2F)2 (LiFSI), LiBF4, LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB), LiBF2C2O4 (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO2F2, LiFSO3, and LiF, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery. The primary lithium salt and secondary lithium salt are distinguished from each other by their different contents.

[0062] In some embodiments, the primary lithium salt is lithium hexafluorophosphate or LiFSI, the content of which is 8-20 wt% based on the total weight of the electrolyte, and the secondary lithium salt is at least one of lithium difluoro(oxalato)borate LiBF2C2O4 (LiDFOB), LiBF4, LiB(C2O4)2 (LiBOB), and lithium difluorobis(oxalato)phosphate (LiDFOP), and optionally LiDFOB or LiDFOP, the content of which is 0.001 wt%-2 wt% based on the total weight of the electrolyte, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0063] In some preferred embodiments, the molar concentration b of the lithium salt in the electrolyte is 0.6 to 1.5 mol / L.

[0064] In some embodiments, the solvent comprises a cyclic ester and a linear ester, the cyclic ester content being 5-40% by mass of the solvent and the linear ester content being 60-95% by mass of the solvent, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0065] In some embodiments, the cyclic ester is ethylene carbonate (EC), propylene carbonate (PC) or a combination thereof, and the linear ester comprises dimethyl carbonate (DMC), thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0066] In some embodiments, the linear ester may further include, in addition to DMC, at least one selected from diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl formate, methyl acetate (MA), ethyl acetate (EA), butyl acetate, acetonitrile (SN), methyl propionate, ethyl propionate (EP), methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, and combinations thereof, and optionally diethyl carbonate DEC, ethyl acetate EA, methyl acetate MA, acetonitrile SN, ethyl propionate EP, and combinations thereof, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0067] In one preferred embodiment, the cyclic ester is ethylene carbonate (EC) and the linear esters include dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC).

[0068] In some embodiments, the percentage (b%) of the linear ester in the solvent relative to the solvent mass and the ionic conductivity (a) (mS / cm) of the electrolyte satisfy the relationship: 8≦a+3b%≦16, and optionally 9≦a+3b%≦15, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0069] In some embodiments, the positive electrode comprises a current collector and an active positive electrode layer deposited on at least one surface of the current collector, the active positive electrode layer comprising an active positive electrode material having the formula LiNi x Co y Q z M 1-x-y-zO2 ternary material, where Q is Mn or Al, M is at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0≦x<1, and optionally 0.5≦x<1, 0≦y≦1, 0≦z≦1, and x+y+z≦1, thereby further improving the high-rate fast charging capability and cycle performance of the battery.

[0070] A second aspect of the present application provides a power consuming device comprising the secondary battery described in the first aspect of the present application.

[0071] The lithium ion battery and power consuming device of the present application will now be described with appropriate reference to the drawings.

[0072] Generally, a lithium ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are absorbed and released by shuttle between the positive electrode and the negative electrode. The electrolyte serves to conduct ions between the positive electrode and the negative electrode. The separator is installed between the positive electrode and the negative electrode, and mainly serves to prevent short circuit between the positive and negative electrodes and allows ions to pass through.

[0073] positive electrode The positive electrode includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material. The positive electrode active material is represented by the formula LiNi x Co y Q z M 1-x-y-z O2 ternary material, where Q is Mn or Al, and M comprises at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0≦x<1, optionally with 0.5≦x<1, 0≦y≦1, 0≦z≦1, and x+y+z≦1.

[0074] For example, a positive electrode current collector has two opposing surfaces in the thickness direction of the positive electrode current collector, and a positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0075] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, an aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material on a polymer substrate. Here, the metal material includes, but is not limited to, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. The polymer substrate includes, but is not limited to, (e.g., substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0076] In some embodiments, the positive electrode active material is lithium nickel cobalt oxide, lithium nickel cobalt manganese oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (may be abbreviated as LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (may be abbreviated as LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O2), LiNi 1 / 3 Co 1 / 3 Al 1 / 3At least one of O2 or its modifying compounds, preferably NCM 622 However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0077] In some embodiments, the positive electrode active material may further include other positive electrode active materials for batteries known in the art. For example, the other positive electrode active materials may include at least one of lithium-containing phosphates with an olivine structure, lithium cobalt oxides (e.g., LiCoO2), lithium nickel oxides (e.g., LiNiO2), lithium manganese oxides (e.g., LiMnO2, LiMn2O4), lithium manganese cobalt oxides, lithium nickel manganese oxides, and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0078] In some embodiments, the weight ratio of the positive electrode active material in the positive electrode membrane layer is 80 to 100% by weight based on the total weight of the positive electrode membrane layer.

[0079] In some embodiments, the positive electrode membrane layer further optionally includes an adhesive. For example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. The weight ratio of the adhesive in the positive electrode membrane layer is 0 to 20% by weight based on the total weight of the positive electrode membrane layer.

[0080] In some embodiments, the positive electrode membrane layer further optionally includes a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, carbon black (e.g., acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode membrane layer is 0 to 20% by weight based on the total weight of the positive electrode membrane layer.

[0081] In some embodiments, the positive electrode may be manufactured by the following method: Components for manufacturing the positive electrode, such as a positive electrode active material, a conductive agent, an adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry having a solid content of 40 to 80 wt %, and the viscosity at room temperature is adjusted to 5000 to 25000 mPa s. The positive electrode slurry is coated on the surface of a positive electrode current collector, dried, and then cold pressed with a cold press to form a positive electrode, and the unit areal density of the positive electrode powder coating is 12 to 26 mg / cm. 2 The compaction density of the positive electrode is 2.0 to 3.6 g / cm 3 and optionally, 2.3 to 3.5 g / cm 3 The formula for calculating the compaction density is: Compaction density = density of coated surface / (thickness after extrusion - thickness of current collector).

[0082] negative electrode The negative electrode includes a negative electrode current collector and a negative electrode film layer (also called a negative electrode active material layer) disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material. The active material layer includes a first active material layer including a first negative electrode active material, and a second active material layer including a second negative electrode active material, which is attached to a surface of the first active material layer away from the current collector. The negative electrode includes the technical features related to the negative electrode described above in this application.

[0083] For example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0084] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, the metal foil sheet may be a copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate. Here, the metal material includes, but is not limited to, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc., and the polymer substrate includes, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0085] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicone-based material, tin-based material, and lithium titanate. The silicone-based material may be selected from at least one of silicone, silicone oxide, silicone carbon composite, silicone nitrogen composite, and silicone alloy. The tin-based material may be selected from at least one of tin, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative electrode active material may be used. These negative electrode active materials may be used alone or in combination of two or more. The weight ratio of the negative electrode active material in the negative electrode film layer is 70 to 100% by weight based on the total weight of the negative electrode film layer.

[0086] In some embodiments, the negative electrode active material comprises at least one of natural graphite, synthetic graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon, silicon-carbon composite, silicon oxide, or compositions thereof.

[0087] In some embodiments, the negative electrode active material is natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithiated TiO2-Li4Ti5O with spinel structure. 12 , Li-Al alloys.

[0088] In some embodiments, the first negative electrode active material is natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithiated TiO2-Li4Ti5O with spinel structure. 12 , Li-Al alloy, and the second negative electrode active material is at least one of natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithiated TiO2-Li4Ti5O having a spinel structure. 12 , Li-Al alloy.

[0089] In some embodiments, the negative electrode active material comprises silicon, the silicon content being 1-10% by weight of the negative electrode active material layer and distributed in at least one of the active material layers.

[0090] In some embodiments, the silicon content (based on SiO2) in the first active material layer is 0 to 25% based on the weight of the first active material layer, and the silicon content (based on SiO2) in the second active material layer is 0 to 25% based on the weight of the second active material layer.

[0091] In some embodiments, the negative electrode membrane layer further optionally includes an adhesive, which may be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The weight ratio of the adhesive in the negative electrode membrane layer is 0 to 30% by weight based on the total weight of the negative electrode membrane layer.

[0092] In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, carbon black (e.g., acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the negative electrode film layer is 0 to 20% by weight based on the total weight of the negative electrode film layer.

[0093] In some embodiments, the negative electrode membrane layer further optionally includes other auxiliary agents, such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)). The weight ratio of the other auxiliary agents in the negative electrode membrane layer is 0 to 15% by weight based on the total weight of the negative electrode membrane layer.

[0094] In some embodiments, the negative electrode may be manufactured by the following method. The components for manufacturing the negative electrode, such as the negative electrode active material, conductive agent, adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry with a solid content of 30 to 70 wt %, and the viscosity at room temperature is adjusted to 2000 to 10000 mPa s. The obtained negative electrode slurry is coated on a negative electrode current collector, and after a drying process, the negative electrode is obtained by cold pressing, for example, by rolling. The unit surface density of the negative electrode powder coating is 6 to 16 mg / cm. 2 The compaction density of the negative electrode is 1.2 to 2.0 g / cm 3 It is.

[0095] The porosity P of the negative electrode active material layer may be obtained by a gas replacement method, and is expressed as porosity P=(V1-V2) / V1×100%, where V1 represents the apparent volume of the negative electrode active material layer and V2 represents the actual volume of the negative electrode active material layer.

[0096] The mass M of the negative electrode active material in the negative electrode active material layer per unit area may be obtained by weighing using a standard balance.

[0097] The thickness T of the negative electrode active material layer may be measured by a micrometer, for example, a micrometer with model number Mitutoyo293-100 and accuracy of 0.1 μm. It should be noted that the thickness of the negative electrode active material layer in the present invention is the thickness of the negative electrode active material layer in the negative electrode for assembling the battery after cold press compaction.

[0098] electrolyte The electrolyte serves to conduct ions between the positive and negative electrodes.

[0099] The electrolyte includes the technical features described above in this application.

[0100] In some embodiments, the electrolyte comprises a lithium salt, a solvent, and an additive, where the lithium salt comprises a primary lithium salt and a secondary lithium salt.

[0101] In some embodiments, the primary lithium salt is different from the secondary lithium salt, and the primary or secondary lithium salt is each independently selected from lithium hexafluorophosphate (LiPF), lithium bis(fluorosulfonyl)imide (LiN(SOF), LiFSI), lithium tetrafluoroborate (LiBF), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), The lithium fluoride is selected from one or more of lithium trifluoromethanesulfonate (LiTFS), lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB), lithium difluoro(oxalato)borate (LiBF2C2O4, LiDFOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO2F2, LiFSO3, LiF, and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0102] In some embodiments, the primary lithium salt is different from the secondary lithium salt, and the primary or secondary lithium salts are each independently selected from at least one of LiPF6, LiN(SO2F)2 (LiFSI), LiBF4, LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB), LiBF2C2O4 (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO2F2, LiFSO3, and LiF. The primary and secondary lithium salts are distinguished by their different amounts.

[0103] In some preferred embodiments, the primary lithium salt is lithium hexafluorophosphate or LiFSI, the content of which is 8-20 wt % based on the total weight of the electrolyte, and the secondary lithium salt is at least one of lithium difluoro(oxalato)borate LiBF2C2O4 (LiDFOB), LiBF4, LiB(C2O4)2 (LiBOB), and lithium difluorobis(oxalato)phosphate (LiDFOP), and optionally LiDFOB or LiDFOP, the content of which is 0.001 wt %-2 wt % based on the total weight of the electrolyte.

[0104] In some preferred embodiments, the molar concentration b of the lithium salt in the electrolyte is 0.8 to 1.2 mol / L.

[0105] In some embodiments, the solvent comprises a cyclic ester and a linear ester, the cyclic ester content being 5-40% by weight of the solvent and the linear ester content being 60-95% by weight of the solvent.

[0106] In some embodiments, the cyclic ester is ethylene carbonate (EC), propylene carbonate (PC), or a combination thereof, and the linear ester comprises dimethyl carbonate (DMC).

[0107] In some embodiments, the linear ester may further comprise, in addition to DMC, at least one selected from diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl formate, methyl acetate (MA), ethyl acetate (EA), butyl acetate, acetonitrile (SN), methyl propionate, ethyl propionate (EP), methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, and combinations thereof, optionally diethyl carbonate DEC, ethyl acetate EA, methyl acetate MA, acetonitrile SN, ethyl propionate EP, and combinations thereof.

[0108] In one preferred embodiment, the cyclic ester is ethylene carbonate (EC) and the linear esters include dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC).

[0109] In some embodiments, the additive includes a carbonate (e.g., fluoroethylene carbonate FEC), a sulfate ester (e.g., vinyl sulfate DTD), and a sulfonate ester (e.g., 1,3-propane sultone PS). The carbonate includes at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The sulfate ester includes at least one of vinyl sulfate (DTD), diethyl sulfate (DES), dimethyl sulfate (DMS), and 4,4-bis(1,3,2-dioxathiolane)-2,2,2,2-tetraoxide.The sulfonate ester includes at least one of 1,3-propane sultone (1,3-PS), propene sultone (PES), 3-fluoro-1,3-propane sultone (FPS), and vinyl methane disulfonate (MMDS).

[0110] In some preferred embodiments, the additives include fluoroethylene carbonate (FEC), vinyl sulfate (DTD), and 1,3-propane sultone (1,3-PS).

[0111] In some preferred embodiments, the mass percentage content of the additive based on the total mass of the electrolyte is 0 to 7%.

[0112] In some embodiments, the electrolyte solution may further optionally include other additives, for example, the other additives may include an anode film-forming additive and a cathode film-forming additive, and may further include additives that can improve some performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high temperature or low temperature performance of the battery, etc.

[0113] Separator In some embodiments, the secondary battery further includes a separator. The present application is not particularly limited to the type of separator, and any known porous structure separator having good chemical stability and mechanical stability may be selected.

[0114] In some embodiments, the separator may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single layer film or a multi-layer composite film, without any particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without any particular limitation.

[0115] In some embodiments, the separator has a thickness of 6 to 40 μm, optionally 12 to 20 μm.

[0116] In some embodiments, the positive electrode, negative electrode and separator can be fabricated into an electrode assembly by a winding process or a lamination process.

[0117] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0118] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0119] The present application is not particularly limited to the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, FIG. 1 shows a secondary battery 5 with a rectangular structure as an example.

[0120] In some embodiments, referring to FIG. 2, the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround and form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be installed on the opening to seal the receiving cavity. The positive electrode, the negative electrode and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. An electrolyte is infiltrated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select it according to actual needs.

[0121] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, with the specific number being selectable by one skilled in the art depending on the application and capacity of the battery module.

[0122] In the battery module, the secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module, or may be arranged in any other manner. Furthermore, the secondary batteries 5 may be fixed by fasteners.

[0123] Optionally, the battery module may further include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0124] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by one skilled in the art according to the application and capacity of the battery pack.

[0125] The battery pack may include a battery box and a plurality of battery modules installed in the battery box. The battery box may include an upper housing and a lower housing, and the upper housing may be covered by the lower housing to form a sealed space for accommodating the battery modules. The plurality of battery modules may be arranged in the battery box in any manner.

[0126] The present application further provides a power consuming device, the power consuming device including at least one of the secondary battery, the battery module, or the battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0127] The power consumption device can be a secondary battery, a battery module, or a battery pack depending on its usage demand.

[0128] 3 shows an example of a power consumption device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be used to meet the demand for high power and high energy density of the secondary battery of the power consumption device.

[0129] Other exemplary devices may be mobile phones, tablet computers, notebook computers, etc. These devices are generally required to be thin and can use secondary batteries as their power source.

[0130] Working Example In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be described in more detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature, and is not any limitation on the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application.

[0131] In the examples, unless a particular technique or condition is specified, it is carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. Reagents or equipment used are not specified by manufacturer and are all conventional products that are commercially available.

[0132] 1. Example Example 1 1. Electrolyte preparation: The electrolyte was prepared in an argon gas glove box with a water content of <10 ppm. Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 3:4:3, and then 1 mol / L of the main lithium salt LiPF6, 1 wt% of the secondary lithium salts LiDFOB+LiPO2F2, and 5 wt% of the additives FEC+DTD were added and mixed uniformly to obtain the electrolyte. The concentration of the lithium salt was 1 mol / L. The ionic conductivity of the electrolyte was 10 mS / cm.

[0133] 2. Manufacturing of positive electrode plate: Ternary material for positive electrode active material LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, polyvinylidene fluoride as an adhesive, and acetylene black as a conductive agent were mixed in a weight ratio of 98:1:1 and dissolved in N-methylpyrrolidone (NMP) as a solvent to produce a positive electrode slurry. The slurry was then applied onto an aluminum foil current collector, and after drying, cold pressing, deburring, cutting, slitting, etc. were performed to produce a positive electrode plate with a size of 87*665mm, which was kept as a spare.

[0134] 3. Negative electrode plate manufacturing: The negative electrode active material graphite, SiO2, the adhesive styrene butadiene rubber, and the dispersant sodium carboxymethyl cellulose were dissolved in deionized water in a weight ratio of 92.8:5:1.2:1 to form a negative electrode slurry. A 6 um copper foil was used as the negative electrode current collector, and the first layer of the negative electrode slurry was coated on the negative electrode current collector to a coating weight of 4.25 mg / cm. 2 After the first active material layer was dried, a second negative electrode slurry was applied, and the negative electrode active material graphite, SiO2, the adhesive styrene butadiene rubber, and the dispersant sodium carboxymethyl cellulose were dissolved in deionized water in a weight ratio of 92.8:5:1.2:1 to form a second negative electrode slurry. The coating weight of the second active material layer was 4.25 mg / cm. 2 A second active material layer was formed.

[0135] The composite negative electrode plate is obtained by sequentially drying, cold pressing, and cutting. After cold pressing, the thickness of the composite active material layer coated on one surface of the copper foil is 51 um, and the compaction density of the active material layer is 1.65 g / cm 3 It is.

[0136] 4. Separator The separator substrate was made of 8 μm thick polyethylene (PE), and a 2 μm thick aluminum oxide ceramic layer was coated on each side of the separator substrate. Finally, 2.5 mg of adhesive polyvinylidene fluoride (PVDF) was coated on each side of the ceramic layer and dried.

[0137] 5. Battery assembly: The positive electrode plate, separator, and negative electrode plate were wound or stacked in that order, with the separator between the positive and negative electrodes to obtain a bare cell. The bare cell was then placed in an exterior body, and 9.5 g of the above-prepared electrolyte was injected into the dried cell. After leaving the cell to stand, forming, shaping, and other processes, a lithium-ion secondary battery with a capacity of 3100 mAh was obtained.

[0138] The manufacturing steps of Examples 2 to 27 and Comparative Examples 1 to 6 were similar to those of Example 1, but the materials or compositions of the electrolyte or negative electrode were changed, and Table 1 was referred to.

[0139] Parameter Test 1. Porosity P% test of negative electrode active material layer The porosity P% of the negative electrode active material layer was measured as follows. Using an inert gas with a small molecular diameter, such as helium gas or nitrogen gas, the actual volume of the sample to be measured was obtained by accurate measurement using a substitution method, and the porosity of the sample to be measured was obtained by combining with Bohr's law (PV=nRT). The porosity P=(V11-V12) / V11×100%, where V11 represents the apparent volume of the negative electrode active material layer, and V12 represents the actual volume of the negative electrode active material layer.

[0140] 2. Test method for average distribution of width:length ratio of negative electrode active material particles The width:length ratio of the negative electrode active material can be obtained by dynamic particle image analysis (eg, using a Sympatec QICPIC dynamic particle image analyzer).

[0141] [Table 1]

[0142] Second, battery performance test 1. Lithium-ion battery CB value test The test method for the lithium release capacity of the positive electrode is as follows: Disassemble the battery in the MBRAUN Robe Box PRS340 / 11-119-11, take out the positive electrode plate, and assemble it into a CR2430 type half coin cell with a positive electrode-lithium strip. The positive electrode plate area used is a mm 2 Here, the electrolyte is a solution of 1M LiPF6 used with EC / EMC / DEC=3 / 5 / 2, and the assembled half coin cell is left to stand for 3 hours and tested at 25°C. First, charge at 0.1C in the voltage range of 2.5~eV to perform lithium desorption, where e is the upper limit voltage of the cell design, and discharge at 0.05C to 2.5V to perform lithium absorption. Then, cycle twice. The discharged coin cell capacity in the second cycle is Y mAh. The length of the positive electrode film in the actual battery design is b mm, the width is c mm, and the number of surfaces coated with the positive electrode active material on the positive electrode current collector is d. The lithium desorption capacity of the positive electrode is X=Y / a*b*c*d.

[0143] The test method for the lithium absorption capacity of the negative electrode is as follows: Disassemble the battery in the MBRAUN Robe Box PRS340 / 11-119-11, take out the negative electrode plate, and assemble it into a CR2430 type half coin cell with a negative electrode-lithium strip. The negative electrode plate area used is f mm 2Here, the electrolyte is a solution of 1M LiPF6 used in EC / EMC / DEC=3 / 5 / 2, and the assembled half coin cell is left to stand for 3 hours and tested at 25°C. First, discharge at 0.1C in the voltage range of 2V~0V to absorb lithium, and then charge at 0.05C up to 2V to remove lithium. The cycle is repeated twice, and the discharged coin cell capacity in the second cycle is Z mAh. The length of the negative electrode film in the actual battery design is h mm, the width is i mm, and the number of surfaces coated with the negative electrode active material on the negative electrode current collector is d. The lithium absorption capacity of the negative electrode is W=Z / f*h*i*d.

[0144] CB=W / X.

[0145] 2. Charging energy power test Rate performance test (charging test to 80% SOC): The test temperature was adjusted to 35℃, and the lithium-ion battery was charged at xC rate (x is 0.5, 0.8, 1, 1.2, 1.5, 2, 2.5, 3) and discharged at 1C. The charging rate was increased in sequence, and the anode potential of 0V was set as the charging stop condition. The maximum charging rate that could be achieved within the range of 0~10% SOC, 10~20% SOC, 20~30% SOC, 30~40% SOC, 40~50% SOC, 50~60% SOC, and 60~70% SOC was obtained, and the charging time (min) required for 0~80% SOC was calculated based on the results.

[0146] 3. Cycle performance test At 25°C, the secondary battery was charged at a constant current of 1C to 4.3V, and then the constant voltage charging was continued until the current reached 0.05C. At this time, the secondary battery was in a fully charged state, and the charging capacity at this time, i.e., the first charging capacity, was recorded. After leaving the secondary battery stationary for 5 minutes, it was discharged at a constant current of 1C to 2.8V. This was one cycle charging and discharging process, and the discharging capacity at this time, i.e., the first discharging capacity, was recorded. The secondary battery was subjected to a cycle charging and discharging test according to the above method, and the discharging capacity after each cycle was recorded. The capacity retention rate (%) after the secondary battery was cycled 600 times at 45°C = discharging capacity after 600 cycles / first discharging capacity x 100%.

[0147] 3. Test results of each embodiment and comparative example According to the above-mentioned method, the batteries of the examples and comparative examples were manufactured, and the performance parameters were measured. The results are shown in Table 2 below.

[0148] [Table 2]

[0149] As can be seen from the above examples and comparative examples, the lithium ion battery of the present application has good rapid charging capability and capacity retention when the average width:length ratio of the negative electrode active material particles is 0.1 to 1, the electrolyte ionic conductivity is in the range of 7 to 15 mS / cm, and the CB value is 1.1 to 1.5 at the same time. For example, the charging time required for 0 to 70% SOC can be shortened to 7 to 8 minutes, and the capacity retention after 600 cycles is still maintained at 95% or more.

[0150] It should be noted that the present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is merely an example, and any embodiment having substantially the same configuration as the technical idea and achieving the same effect within the scope of the technical solution of the present application is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiment and other methods configured by combining some of the components in the embodiment are also included in the scope of the present application, within the scope of the purpose of the present application. [Explanation of symbols]

[0151] 5, secondary battery, 51, case, 52, electrode assembly, 53, cover plate, 6, power consuming device.

Claims

1. A lithium ion battery comprising a positive electrode, a negative electrode, and an electrolyte, the negative electrode comprising a negative electrode current collector, and a negative electrode active material layer comprising a negative electrode active material deposited on at least one surface of the negative electrode current collector, wherein an average width:length ratio of particles of the negative electrode active material is 0.1 to 1, the ionic conductivity of the electrolyte is 7 to 15 mS / cm, and a ratio CB of the lithium occlusion capacity of the negative electrode to the lithium desorption capacity of the positive electrode is 1.05 to 1.

5.

2. 2. The battery according to claim 1, wherein the current of the positive electrode is four or more times the lithium release capacity per unit time during the charging process from 0% to 70%.

3. 3. The battery according to claim 1, wherein an average current during charging of the battery from a 0% charged state to an 80% charged state is four or more times the lithium release capacity of the positive electrode per unit time.

4. 4. The battery according to claim 1, wherein the negative electrode active material layer has a porosity of 20 to 60%.

5. The compaction density of the negative electrode active material layer is 1.2 to 1.9 g / cm ３ and the coating weight is 5 to 18 mg / cm ２ 5. The battery according to claim 1, wherein

6. 6. The battery according to claim 1, wherein the negative electrode active material comprises natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon, a silicon-carbon composite, silicon oxide, or a composition thereof.

7. 7. The battery according to claim 1, wherein the negative electrode active material layer has a thickness of 30 to 150 μm.

8. 8. The battery according to claim 1, wherein the negative electrode active material layer comprises a first active material layer containing a first negative electrode active material, and a second active material layer containing a second negative electrode active material attached to a surface of the first active material layer away from the current collector.

9. The average volume particle size D of the first negative electrode active material ｖ５０ is the average volume particle size D of the second negative electrode active material ｖ５０ 9. The battery of claim 8, wherein the

10. 10. The battery according to claim 8, wherein the first negative electrode active material layer has a greater compaction density than the second negative electrode active material layer.

11. 11. The battery according to claim 1, wherein the electrolyte solution comprises a lithium salt, a solvent and an additive, and the lithium salt comprises a main lithium salt and a sub lithium salt.

12. The primary lithium salt is different from the secondary lithium salt, and the primary lithium salt or the secondary lithium salt is independently LiPF ６ , LiN(SO ２ F) ２ , LiBF ４ , LiN(CF ３ SO ２ ) ２ , LiClO ４ , LiAsF ６ , LiB(C ２ O ４ ) ２ , LiBF ２ C ２ O ４ , lithium difluorobis(oxalato)phosphate, LiPO ２ F ２ , LiFSO ３ 12. The battery of claim 11, wherein the lithium ion is selected from at least one of the following: LiF.

13. The primary lithium salt is lithium hexafluorophosphate or LiFSI, the content of which is 8 to 20 wt % based on the total weight of the electrolyte, and the secondary lithium salt is lithium difluoro(oxalato)borate, LiBF ４ , LiB(C ２ O ４ ) ２ , or lithium difluorobis(oxalato)phosphate, the content of which is 0.001 wt % to 2 wt % based on the total weight of the electrolyte.

14. The battery according to any one of claims 11 to 13, characterized in that the solvent contains a cyclic ester and a linear ester, the content of the cyclic ester being 5 to 40% by mass of the solvent, and the content of the linear ester being 60 to 95% by mass of the solvent.

15. 15. The battery of claim 14, wherein the cyclic ester is ethylene carbonate, propylene carbonate, or a combination thereof, and the linear ester comprises dimethyl carbonate.

16. 16. The battery of claim 15, wherein the linear ester is selected from diethyl carbonate, methyl ethyl carbonate, methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, or combinations thereof.

17. 17. The battery according to claim 11, wherein a percentage (b%) of the linear ester in the solvent relative to the mass of the solvent and an ionic conductivity (a) (mS / cm) of the electrolyte satisfy the relationship: 8≦a+3b%≦16.

18. The positive electrode includes a current collector and a positive electrode active material layer deposited on at least one surface of the current collector, the positive electrode active material having a formula LiNi ｘ Co ｙ Q ｚ M １－ｘ－ｙ－ｚ O ２ 18. The battery of claim 1, comprising a ternary material of the formula: where Q is Mn or Al, M comprises at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0≦x<1, 0≦y≦1, 0≦z≦1, and x+y+z≦1.

19. A power consuming device, comprising a secondary battery according to any one of claims 1 to 18.

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